In the past, various types of the rotary seal-free flow-through coil planet centrifuge devices have been developed, each having a specific advantages for performing particular types of separations. In most of these rotary seal-free flow-through coil planet centrifuge systems, a coiled helical column rotates around the central longitudinal axis of its column holder while simultaneously revolving around a second longitudinal axis i.e., the central axis of the centrifuge, parallel with or perpendicular to the central longitudinal axis. Depending on the relative direction of the rotation about the two axes with respect to one another, different results occur. For example, U.S. Pat. No. 3,755,309 discloses a system that produces exteremely vigorous and even mixing of the column contents, which is particularly suitable for analytical separations with a narrow-bore tubing. U.S. Pat. No. 3,856,669, discloses a horizontal type of coil planet centrifuge, called an elution centrifuge, that produces a stable centrifugal force field which retains viscous low interfacial tension polymer phase systems in the column for performing separations of macromolecules and cell particles.
Inverted orientations of the column holder described in U.S. Pat. No. 4,430,216, produce a unique heterogeneous centrifugal force field that results in a mixing zone in the helical column near the central axis of the centrifuge and a settling zone in the remote portion of the column. This system has been applied to countercurrent chromatography with a high peak resolution, due to the large volume of the stationary phase retained in the column. The system, however, has difficulty with hydrophilic solvent systems such as butanol/acetic acid/water (4:1:5), sec.-butanol/water and aqueous-aqueous polymer phase systems that have a tendency to emulsify. Butanol systems are extremely useful for separation of polar compounds such as peptides and small proteins, while polymer phase systems are ideal for partitioning large proteins and cell particles.
U.S. Pat. No. 3,994,805 discloses a centrifuge which revolves a helical column, at an inclined angle from the vertical, around the central axis of the centrifuge and yet maintains the column in a fixed orientation while it revolves. This centrifuge provides a force field strength between that of the centrifuges described in U.S. Pat. Nos. 3,856,669 and 3,775,309 and causes intermediate partitioning efficiency and stability.